U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY

DELINEATION OF BACKGROUND LABORATORY CONTAMINATION IN THE ANALYSIS OF

TRACE CONCENTRATIONS OF EXTRACTABLE ORGANIC MATERIALS IN CRYSTALLINE

ROCKS BY SOXHLET EXTRACTION, COLUMN CHROMOTOGRAPHY, AND GAS

CHROMATOGRAPHY

By

Koichi Mimura1 and Leigh C. Price2

Open-File Report 99-335 

1999

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial 

standards. Use of brand or trade names in this report are for descriptive purposes only and do not imply 

either endorsement or non-endorsement by the U.S. Government.

Department of Earth and Planetary Sciences, Nagoya University, Nagoya, 464-01, Japan 

2U.S. Geological Survey, Denver Federal Center Denver, CO 80225, USA
1.0 Abstract.................................................................................... 2

2.0 Introduction................................................................................. 2

3.0 Analytical Method......................................................................... 3

4.0 Contamination Checks..................................................................... 5

4.1 Solvents................................................................................ 5

4.11 Dichloromethane............................................................ 6

4.12 Hexane....................................................................... 11

4.13 Benzene...................................................................... 14

4.14 Benzene Methanol.......................................................... 14

4.2 Apparatus........................................................................... 19

4.21 Glassware............................................................... 19

4.22 Cone Vial Cap.......................................................... 19

4.23 Rubber Bulb............................................................ 19

4.24 Copper Strips............................................................ 21

4.25 Alumina/Silica-Gel Columns... ..................... .................. 21

4.26 Cardboard Storage Cartons............................................ 26

4.27 Rock Crushing and Powdering........................................ 29

4.271 Bull Quartz.................................................. 29

4.272 Flint-Glass Bottle........................................... 29

4.273 Source-Rock Heating....................................... 29

4.28 The Cleaning Sand...................................................... 29

4.29 Procedure Blanks........................................................ 36

4.291 Bull Quartz........:.......................................... 36

4.292 Flint-Glass Bottle........................................... 38

5.0 Real World Example: Mantle Xenolith ................................................. 40
1.0 ABSTRACT

Contamination checks were carried out for sample preparation, Soxhlet extraction and 

the subsequent analyses of extracted bitumen, from high-grade metamorphic and igneous rocks, carbonaceous 

rocks from ore deposits, and other crystalline rocks. We examined possible contamination from solvents, 

laboratory apparatus, and from most of the analytical steps of the total procedure. The results of our 

examination were as follows: Once-distilled dichloromethane, twice distilled hexane, twice distilled benzene, 

and HPLC-grade methanol were pure enough to be used as solvents. No contaminants were leached from the 

septa of the cone vials used for the automated sampler on our gas chromatograph by hexane, benzene, or 

dichloromethane. Activated copper strips (used to remove sulfur during extraction) did not produce organic 

contamination by reacting with dichloromethane. However, new copper strips had to be rinsed with 

dichloromethane before their use, because the copper strips had a surficial wax coating from their 

manufacture. Saturated and aromatic hydrocarbon (HC) fractions from blank alumina/silica-gel column 

chromatography had only negligible peaks. Glass bottles with foil-lined caps should always be used for 

sample storage, because of possible wax contamination from cardboard products. Obviously, if samples are 

to be cut with a saw, it should be done in a pre-cleaned water-based system.

We compared the saturated- and aromatic-HC and resin gas chromatograms from a mantle 

xenolith to those from a blank procedural check, to determine indigenous organic materials in the mantle 

xenolith. This comparison demonstrated that we can quantitatively and qualitatively analyze organic 

materials at very low concentrations (0.1 to 0.5 ppm total bitumen by weight). This comparison also 

demonstrated that the contaminates in the saturated- and aromatic-HC fractions are negligible. Thus, as 

demonstrated by the results herein, our Soxhlet extraction procedure has been optimized for analysis of 

small concentrations of exotic indigenous organic compounds in very high-rank crystalline rocks.

' 2.0 INTRODUCTION

In organic geochemistry, we use many different organic solvents and different multi-step 

methodologies to quantitatively and qualitatively analyze organic compounds. For example, in extracting 

organic materials from oil-source rocks, we may use several solvents (chloroform, iso-octane, benzene, 

methanol, etc.) and several steps (crushing and grinding, extraction, evaporation, fraction-separation 

chromatography, gas chromatography, etc.). Some of these steps also use different organic solvents. The 

concentration of any organic contaminant that is in the organic solvents and is added to the sample extracts 

during any one of these steps, will increase with increasing volume of the solvents used in that procedure, 

since we can never make an absolutely pure mono-compound organic solvent. The possibility that the 

extract can become contaminated also increases with the increasing number of ancillary analytical 

methodologies. Thus, we cannot completely eliminate contamination from any given procedure, because 

we must use several different organic solvents and complex methodologies to carry out organicgeochemical analyses. However, for every sample there is a contaminant concentration which is acceptable 

as a maximum concentration for that sample, and that contaminant concentration depends on the 

concentration of indigenous organic materials in a sample. For example, normal petroleum-geochemical 

analyses involve relatively high concentrations of bitumen extracted from shales, or oils, and thus 

acceptable contaminant levels can be relatively high. On the other hand, the maximum contaminant 

concentration for analysis of our crystalline rock samples will, a priori, have to be very low, because highgrade metamorphic rocks, igneous rocks, and rocks from ore deposits contain only moderate (10-200 ppm 

by weight) to low (0.05 to 1 ppm by weight) concentrations of organic materials . To extract indigenous 

organic materials in those rocks and obtain useful quantitative and qualitative information about the
extracted organic materials, we must therefore use high-purity organic solvents, absolutely clean apparatus, 

and methodologies which exclude ambient contamination in the laboratory environment.

In this paper, we mainly tried to determine the highest-quality organic solvents possible, and to also 

delineate the degree of low-level contamination resulting from our Soxhlet extraction procedure. We thus 

researched the following three points in our procedure: 1) organic-solvent purity, 2) possible 

contamination resulting from the apparatus used, and 3) possible contamination resulting from the separate 

steps in our procedure. Finally, we illustrate the strengths and limitations of our procedure with a rock 

sample (a mantle xenolith) from the natural system that contains a very small concentration of extractable 

organic compounds.

In this paper we: 1) demonstrate the minimal levels of contamination which are associated with 

our analytical procedure; and 2) provide the details of our analytical procedure, so that other laboratories 

may replicate our results in the study of low concentrations of organic compounds in high-rank crystalline 

rocks. Because of the many possible pitfalls in such research, from many different possible sources of 

laboratory contamination, successfully carrying out these analyses is not a straight-forward task.

As an aside, we are not aware of any published study similar to this one, which has examined 

laboratory background contamination levels for the typical analyses normally carried out in petroleum 

geochemistry. Thus, this paper also serves to fill that void.

3.0 ANALYTICAL METHOD

In the study of metamorphic rocks, igneous rocks, and rocks from ore deposits, we use the 

following methodology: The surfaces of rock samples may, or may not, be cut off with a rock cutter, or a 

rock sample may, or may not, be cut with a cutting saw (water obviously being used as the cutting fluid). 

In any case, the original or trimmed rock is thoroughly rinsed with dichloromethane from a squirt bottle to 

remove any contaminants which the sample may have taken up from either laboratory or outcrop 

surroundings. The rinsed sample is crushed and ground with a jaw crusher and a ball mill, respectively. 

Both the jaw crusher and ball mill are thoroughly cleaned before use. The powdered sample is sieved to 

100 or 200 mesh and the powder is stored in glass jars (previously baked at 400°C) with tin foil in their 

lids. For Soxhlet extraction, a weighed amount of powder is placed in a glass-fiber Soxhlet thimble which 

was previously baked at 450°C for 12 hours. The powder is extracted for 10 or 21 days using 1000 ml of 

dichloromethane. Boiling chips, and copper strips activated with hydrochloric acid, are placed in the 

round-bottom flask so that the solvent will boil smoothly and any free sulfur will be removed from the 

extract. If the volume of dichloromethane in the round bottom flask decreases, new dichloromethane is 

added to the system. We have found that wrapping all fritted-glass joints in the Soxhlet extractor with 

Teflon tape minimizes solvent loss during the extraction. This loss rninimization, in turn, rninimizes the 

need to add solvent during the long (10-21 days) extraction times. We have documented that the more 

solvent added to the system during extraction, the greater the introduction of low-boiling contaminants to 

the extract during the extraction process.

On completion of the extraction, the solvent and extract in the round-bottom flask are filtered .with 

an all-glass filtering apparatus using GF/A silica-fiber paper over a fritted-glass filter. The filtered 

solution is caught in another round-bottom flask and from there is transferred to a 600 to 1000 ml heavywalled beaker, for passive evaporation. All solvent transfers are quantitative. The filtering apparatus and 

the bank of 12 Soxhlet extraction units are dedicated only for extracts from crystalline rocks. Sedimentary 

rocks are extracted in another bank of Soxhlet extractors and processed in separate apparatus. Soxhlet

4
extractors and processing apparatus dedicated solely for use with rocks with very low concentrations of 

organic compounds are an absolute requirement to minimize contamination. All glassware that comes in 

contact with solvent and extract is baked at 400°-450°C for 12-24 hours and rinsed with dichloromethane 

just before use.

The filtered extract is passively evaporated (Price and Wenger, 1992) to 15-20 ml by leaving the 

beaker in a fume hood with the sash up and the fan off. When the solvent level reaches around 50 ml, the 

beakers are tilted on the vertical axis by putting props under the beakers, thus concentrating the solvent and 

extract to one side of the beaker. This prevents excessive loss of Cn- compounds from the extract during 

the last stages of solvent evaporation. When the solvent level reaches 20 ml, the solvent and extract are 

quantitatively transferred, with transfer pipettes, to an 8 dram vial. The solvent is then further passivelyevaporated to 1 ml by leaving the 8 dram vial open in the fume hood (sash up, fan off). The 

dichloromethane is then replaced by hexane by adding 2 ml of hexane and passively evaporating the extract 

and solvent to 1 ml. This process is repeated thrice, causing the precipitation of small amounts of material 

insoluble in hexane (not asphaltenes in the usual petroleum-geochemical meaning). This material is filtered 

from the hexane using a small metal-filter assembly dedicated only for the crystalline rocks. The 

precipitate is mobilized from the filter with CH2Cl2 and caught in a tared vial, taken to" dryness, and 

weighed. The previously-filtered bitumen is passively evaporated to 0.5 ml, and is thus ready for fraction 

separation by column chromatography.

The extract is separated by alumina/silica-gel column chromatography into three fractions; 

saturated hydrocarbons (HCS), aromatic HCS, and "resins". Each of the three fractions is split equally 

into two parts using 10 ml volumetric flasks and 5 ml pipettes. One 5 ml spilt is used for weighing the 

Ci2+ organic materials in each of the three dried fractions to determine the concentrations of extracted 

organic materials. The other part is used for qualitative analysis of the Cg+ organic materials by flame 

ionization detection (FID) gas chromatography and/or mass spectrometry. The splits of each fraction are 

passively condensed to 500 (j.1, and 300 jil of the condensed 500 (j.1 is subsequently evaporated to a volume 

dependent on the amount of organic material contained in the sample. The 300 u.1 split can be evaporated 

to as low as 5 jil when a rock sample has very low concentrations of organic materials.

The analytical conditions of the flame-ionization-detection gas chromatograph are as follows: One 

(j.1 of sample is injected into the gas chromatograph inlet by the splitless method. The temperature of the 

inlet is 340°C. The column is a 60 m x 0.32 mm capillary column (Phenomex Zebron, ZB -1) coated with 

a 0.25 (j.m layer of 100% methyl polysiloxane. The flow rate of the helium carrier gas is 2.2 ml/min. The 

oven temperature-program is 50° to 330°C at 4.5°C/min., followed by 15 min. at 330°C. The detector 

temperature is at 350°C. Flow rates of H2, air, and make up gas (He) at the FID are 40, 380, and 28.5 

ml/min, respectively.

4.0 CONTAMINATION CHECKS 

4.1 SOLVENTS

We again note that use of brand or trade names in this report is for descriptive purposes only and 

does not imply either endorsement or non-endorsement by the U.S. Geological Survey.

The purpose of the solvent checks was to determine: 1) the concentrations and compositions (if 

possible) of the different contaminants in the various solvents employed in our method; 2) the various
maximum concentrations which these contaminants are increased to, due to the various evaporative steps in 

our method; and 3) which solvents can be successively distilled for use in our studies of organic materials 

in various crystalline rocks. At the outset, we note that the purity of the different solvents we discuss 

herein is usually high enough for normal analytical procedures with extracts from sedimentary rocks. 

However, due to both the large amount of solvent we use (1000 to 3000 ml depending on the sample and 

the extraction times), and the low volumes to which one-half of the extract can be reduced for gas 

chromatography (500 to 1500 ml can be reduced as little as 20 jil for a 75,000 fold decrease in solvent 

volume in some cases), the differences in low-boiling contaminants between the various solvents becomes 

paramount.

In the following discussions, we have not measured, or even estimated, absolute concentrations of 

the different contaminants we found in our study, nor have we attempted to qualitatively identify most of 

the contaminant compounds. Both of these tasks would require substantial effort and would not contribute 

significantly to the paper. In this study, discussion of the relative concentrations of contaminant peaks 

among the different samples we have analyzed adequately serves our purposes. However, so that the 

reader may have some rough estimates of concentrations, we include the following: We normally perform 

gas chromatographic analyses of saturated-HC fractions at solvent concentrations of 8 mg/ml of GU+ 

material, or about 8,000 ppm (see Figure Ig for an example). The resulting chromatograms of such 

analyses typically have full-scale detector responses of 250 to 550 mV, in the Ci4+ range, depending on the 

sample characteristics, the amount of Ci4- material in the sample, and other variables. In contrast, the 

detection limit for flame ionization detectors is generally about 0.05 ppm. Thus, the smallest peaks at our 

most sensitive detector settings, 40-60 mV, would represent that concentration.

4.11 Dichloromethane

In our study, on average, we use approximately 1200 ml of dichloromethane as the extraction 

solvent. In our procedure, one-half portion of the extract can be condensed to 20 jil when the concentration 

of organic materials is very low in the original sample. This process magnifies the concentration of any 

contaminants in the dichloromethane 600 ml/.020 ml, or 30,000 times. In our check of dichloromethane 

contamination, we used 1200 ml of dichloromethane put in a beaker and passively evaporated to 1 ml. A 

200 jil sample was taken at each volume of 1200, 600, 200, 50, and 10 ml, and a 300 ul sample was taken 

at a CH2Cl2 volume of 1 ml. All these aliquots were taken by syringe and placed in a 300 ul cone vial used 

for our automatic sampler on the gas chromatograph. These six dichloromethanes were condensed to 20 ul 

and analyzed by FID gas chromatography. The levels of volume reduction of these six dichloromethanes 

are shown in Table 1.

We analyzed seven different dichloromethanes: D143-4 (HPLC by Fisher Scientific), D150-4 

(HPLC by Fisher Scientific), D151-4 (OPTIMA by Fisher Scientific), D154-4 (GC Resolve by Fisher 

Scientific), once-distilled D143-4, once-distilled D-150-4 and once-distilled D154-4. Figure 1 shows all the 

gas chromatograms obtained from the different stages of evaporation of the D143-4 dichloromethane. A 

gas chromatogram of the saturated HCS from a typical oil is also included in Figure 1 (Fig. Ig) so that the 

reader may make some judgment of the approximate carbon number of the various contaminants discussed 

in this paper. Vita for the oil are in Price and LeFever (1994, their Table 1). Figure 2 shows gas 

chromatograms for the maximum volume reduction of the D143-4, D150-4, D151-4, D154-4, oncedistilled D143-4, once-distilled D150-4, and once-distilled D154-4 dichloromethanes. The high scales of 

Figure 1 and Figure 2 are adjusted at 1000 and 100 mV, respectively.
Table 1. Levels of volume reduction of the different solvents used in our analytical procedure.

Solvent Volume* (ml)

Dichloromethane 1200

600

200

50

10

1

Hexane 30

15

5

1

Benzene 30

15

5

1

Concentrated rate (times)

1.0x10

2.0x10

6.0x10

2.4 xlO2

1.2xl03

l.SxlO4

1.0 x 10

2.0x10

6.0x10

4.5 x 102

l.Ox 10

2.0 x 10

6.0x10

4.5 x 102

* Volume at which a sample is taken for analysis.
1a

0143-4

x10

High Scale 1000mV

1d

0143-4

x240

High Scale 1000mV

1b

0143-4

x20

High Scale 1000mV

1e

0143-4

x1200

High Scale 1000mV

1c

0143-4

x60

High Scale 1000mV

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

if

0143-4 

X18.000 

High Scale 1000mV

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

19

Crude Oil 

Madison (N8-138) 

High Scale 493mV

20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 1. Gas chromatograms at an attenuation of 1000 mV demonstrating contamination in Fisher 

Scientific D143-4 dichloromethane progressively being concentrated by increasing solvent 

evaporation (la to If). A gas chromatogram (Ig) of the saturated HCS from a Williston Basin mid 

Madison crude oil is shown for calibration of carbon-number versus elution time.
2a

0143-4

x18,000

High Scale 100mV

2d

0154-4

X18.000

High Scale 100mV

2b

01SO-4

x18,000

High Scale 100mV

28

0143-4

Once Distilled

x18,000

High Scale 100mV

2c

01S1-4

x18,000

High Scale 100mV

21

0150-4

Once Distilled

x18,000

High Scale 100mV

10 20 30 40 50 60 

ELUT1ON TIME IN MINUTES

10 20 30 40 50 60 

ELUT1ON TIME IN MINUTES

2g

0154-4

Onca Distilled

x18,000

High Scale 100mV

I Ilk

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 2. Gas chromatograms at an attenuation of 100 mV of four different dichloromethanes at our 

maximum level of evaporation (x 18,000; 2a to 2d) and of single distillations of three of the 

dichloromethanes (2c to 2g) at our maximum level of evaporation. Chromatogram labeling of 2f 

explained in text.
Many peaks appear on the gas chromatograms from the D143-4 solvent (Fig. 1), especially on the 

gas chromatograms of the highest levels of volume reduction (x 1200, Fig. le; and *x 18,000, Fig. If). The 

peak distributions of all the chromatograms in Figure 1 are similar to each other, with the peak height 

increasing with increasing levels of volume reduction of the dichloromethane. This observation 

demonstrates that the organic materials resulting in these peaks are inherent in the dichloromethane (D143- 

4). The principal contaminant peaks in the D143-4 dichloromethane appear between 7 and 10 minutes 

retention time (Fig. 1). However, at the highest levels of volume reduction (x 1200, and x 18,000), high 

concentrations of contaminant peaks are present at retention times as high as 22.5 minutes, which 

corresponds to an elution time between the n-Cn and n-Cu paraffins. Clearly these contaminant levels are 

unacceptable for carrying out organic-geochemical analyses of samples with only very low concentrations 

or organic compounds, eg - the types of samples involved in our studies. In Figure 2, the other three 

dichloromethanes (D 15 0-4, D151-4, and D154-4) had gas chromatograms similar to those of Figure 1, as 

the level of solvent-volume reduction increased. However, the series of chromatograms for those three 

dichloromethanes need not be shown here.

The gas chromatogram of D150-4 is markedly different from that of D143-4 both in peak pattern 

(Figs. Id and 2b) and in the level of contaminant concentration (Figs. 2a and 2b). For example, D150-4 

contains eight large peaks which appear over 7 to 13 minutes (Fig. 2b). In contrast, D143-4 contains a 

different complex of contaminant peaks eluting between 7.5 to 10 minutes (Fig. Id). Please note that the 

level of solvent-volume reduction is markedly different between Figure 2b (x 18,000) and Id (x 240). 

Thus, the concentration of contaminant peaks in D150-4 is very low compared to that of D143-4 (Figs. 2a 

and 2b). Therefore, where the two different dichloromethanes have had the same level of volume reduction 

(x 18,000), and are compared at the same full-scale peak height (eg, 100 mv), the contaminants in the 

D143-4 sample are off scale from 7.5 to 22.5 minutes. On the other hand, the D150-4 sample, has five 

peaks slightly off scale, and clearly has orders of magnitude less contaminant peaks than the D143-4 

dichloromethane. This large difference in contaminant concentrations is at least partly due to stabilizers 

(amylene and cyclohexane) which are added to D143-4, but not to D150-4. Gas chromatograms of the 

D151-4 and D154-4 dichloromethanes with maximal reduced solvent volumes (x 18,000) are similar to 

each other (Figs. 2c and 2d), with contaminant concentrations intermediate to those of the D143-4 and 

D15 0-4 dichloromethanes.

Note that the two peaks labeled "COL" (for column) in Figure 2b at 41.2 and 47.3 minutes are 

contaminant peaks from the gas chromatograph column. These peaks occur sporadically, with variable 

peak heights, in most of our contamination checks and samples. The gas chromatograph which we used in 

this study is a multi-use instrument, used by different personnel in the USGS petroleum geochemistry 

group. Our study was performed over an 11 month time period, during which many other analyses of 

samples, other than our own, were performed on the gas chromatograph by other researchers. The two 

peaks under discussion likely were introduced onto the column by these other samples, and the peaks would 

then later appear in our analyses. Injection of blank benzene, benzene-methanol, or dichloromethane into 

the gas chromatograph would often cause the elution of these two peaks, which would decrease in peak 

height with successive blank injections. The presence of these peaks in our gas chromatograms will not be 

further discussed.

To increase the purity of all the solvents used in our procedure, we distilled all solvents at least 

once in moderately-large (4,000 ml) round bottoms in our laboratory. Figures 2e to 2g show the results of 

these distillations for the D143-4, D150-4, and D154-4 dichloromethanes, respectively. In all three cases, 

solvent volumes have been maximally reduced (x 18,000), and all 3 chromatograms are at 100 mv full

10
scale. The degree of contamination in the once-distilled D143-4 significantly decreases, compared to 

original D143-4 (compare Fig. 2a with Fig. 2e). However, the amount of contamination in the oncedistilled D143-4 is still far too large for our purposes. Note that peaks with the higher retention times (15 

minutes and greater) appear to have been preferentially reduced compared to the peak heights of the lowerboiling contaminants. This is, of course, expected, because organic materials with higher boiling 

temperatures are more easily removed than ones with lower boiling temperatures by distillation. The 

contaminant concentrations in the once-distilled D150-4 (Fig. 2f), and D154-4 (Fig. 2g) dichloromethanes 

become much lower compared to the original contaminant concentration levels (Figs. 2a to 2d).

Moreover, the gas chromatograms of the distilled dichloromethanes have much different peak 

patterns compared to the contaminant peak distributions in the original dichloromethanes. Furthermore, the 

maximum in the peak distribution is shifted from 10 to 7 minutes by distillation. The once-distilled D154-4 

and D143-4 dichloromethanes contain slightly higher concentrations of contaminants with higher-boiling 

temperatures (elution times from 13 to 25 minutes) than does the once-distilled D150-4. We deemed the 

once-distilled D150-4 dichloromethane to be sufficient for our study. In a later section, we will discuss the 

peaks labeled Dl to D9 in the D150-4 gas chromatogram of the dichloromethane D150-4 (Fig. 2f).

4.12 Hexane

In our overall procedure, hexane is used for replacing dichloromethane in our extracts, for making 

silica-gel/alumina columns for fraction-separation column chromatography, and as the solvent to elute the 

saturated HCS during column chromatography. In all these steps, a total of 30 ml of hexane is employed. 

Because half of the 30 ml is condensed to 500 u.1 and is subsequently concentrated 15 times for samples 

with very low concentrations of extractable organic compounds, the maximum concentration of 

contaminant in hexane would be from a solvent volume reduction of 450 times. In this phase of our 

contamination check study, hexane was thus reduced in volume by 450 fold.

Thirty ml of hexane was thus put in a beaker and passively evaporated to 1 ml. Two hundred u.1 of a 

hexane aliquot were taken for a sample at a hexane volume of 30, 15, and 5 ml, and a 300 ul sample was 

taken at 1 ml hexane volume. All four samples were put into cone vials and condensed to 20 u.1 for analysis 

by FID gas chromatography. The concentrated rates of hexanes are listed in Table 1. We so evaluated six 

different hexanes; H302-4 (HPLC by Fisher Scientific), H303-4 (OPTIMA by Fisher Scientific), H334-4 

(Spectranalyzed by Fisher Scientific), H217 (Non-Spectro by Burdick & Jackson), once-distilled H303-4, 

and twice-distilled H303-4. We show gas chromatograms from the H302-4 hexane at all four levels of 

solvent concentration (x 10, x 20, x 60, and x 450) in Figure 3 and gas chromatograms from the other 

hexanes at the solvent volume reduction level of 450 times in Figure 4. The high scales of Figure 3 and 

Figure 4 are adjusted at 1000 and 100 mV, respectively.

There are numerous large peaks on the H302 gas chromatograms with the greatest level of solvent 

reduction (Fig. 3d, x 450) with retention times between 6.5 and 22 minutes. The other hexanes that we 

examined, H217, H303-4, and H334-4, also contained high concentrations of contaminant peaks. 

However, the gas chromatograms from these hexanes for the four differentlevels of solvent reduction will 

not be shown here. The contaminant peak distribution of the H303-4 (Fig. 4c) and H334-4 (Fig. 4d) gas 

chromatograms, is remarkably similar to that of the H302-4 (Fig. 3d) gas chromatogram. However, this is 

not surprising, since these are all Fisher Scientific products which most probably are manufactured from 

the same starting product. However even the H217 gas chromatogram has a peak distribution (Fig. 4b)

11
3 a

H302-4

x10

High Scale 1000mV

y

3b

H302-4

x20

High Scale 1000mV

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

20 30 40 5

ELUTION TIME IN MIN

Figure 3. Gas chromatograms at an attenuation of 1000 mV demonstrating contamination in Fisher Scientif

progressively being concentrated by increasing solvent evaporation.
4a

H302-4

x450

High Scale 100mV

4d

H334-4

X450

High Scale 100mV

4b

H217

x450 .

High Scale 100mV

4e

H303-4

Once Distilled

x450

High Scale 100mV

'4c

H303-4 

' x450 

High Scale 100mV

4f

H303-4

Twice Distilled

X450

High Scale 100mV

20 30 40 50 60 

ELUTION TIME IN MINUTES

70 10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 4. Gas chromatograms at an attenuation of 100 mV of four different hexanes at our maximum level 

of evaporation (x 450; 4a to 4d); and of once-distilled (4e) and twice distilled (4f) H303-4 hexane, 

also at our maximum level of evaporation.

13
somewhat similar to that of the other three hexanes (Figs. 4c, 4d, and 3d), even though the H217 hexane is 

made by a different manufacturer (Burdick & Jackson). This observation is probably due to the fact that 

all high-purity hexane solvents are originally derivatives from crude oil, all (or most) of which have the 

same Ce to CIQ isomers in them. Hence, we might expect to see the similar peak distributions that we do 

see, for these solvent hexanes derived from crude oils.

The original contaminant concentrations in the hexanes decrease in the order of H217=H302- 

4»H334-4>H303-4 (Fig. 4). Note that the level of contaminants is much higher in H217 and H302-4 

than in the other two hexanes (H334-4, and H303-4), which have about the same starting original 

contaminant concentrations. Of the solvent hexanes we examined, twice-distilled H303-4 (twice-distilled in 

our laboratory) proved to provide an adequate solvent for our research. The contaminant concentration in 

the H303-4 hexane dramatically decreased upon a single distillation (compare Fig. 4e (once-distilled) to 

original H303-4 hexane, Fig. 4c). However, contaminant peaks still remained too high for our purposes. A 

second distillation (Fig. 4f) yielded a product appropriate for our needs. We note that the H303-4 hexane, 

is actually a mixture of hexane isomers, and is not just n-Ce (normal hexane). However, that H303-4 was 

an isomer mixture, rather than the single n-Ce isomer, did not detract from its purity as a solvent.

4.13 Benzene

A total of 30 ml of benzene is used with the column chromatography in our procedure. Because 

half of the 30 ml of benzene is condensed to 500 u.1 and is subsequently concentrated 15 times for samples 

with the low concentrations of organic materials, the maximum concentration of contaminants in benzene 

would be 450 times. Thus, in our examination of contaminants in different benzenes, we decreased solvent 

volumes by 450 fold.

Thirty ml of benzene were put in a beaker and passively evaporated to 1 ml. Two hundred ul of 

benzene were withdrawn by syringe at benzene volumes of 30, 15, and 5 ml and, 300 (j.1 were withdrawn at 

1 ml and put into our 300 uL auto-sampler cone vials. These benzenes were condensed to 20 ul and were 

analyzed by FID gas chromatography. The concentrated rates of benzene are listed in Table 1. We 

checked eight different benzenes: B411-4 (Spectranalyzed by Fisher Scientific); JT9154-5 (BAKER 

ANALYZED Reagent by J. T. Baker); JT9256-3 (BAKER ULTRA RESI-ANALYZED by J. T. Baker); 

33291 (Spectrophotometric Grade by Alfa Aesar); 27070 (HPLC grade by Sigma-Aldrich); EM-BX0212- 

1 (OMNISOLV grade by EM Science); once-distilled EM-BX0212-1; and twice-distilled EM-BX0212-1. 

We show gas chromatograms for the B411-4 benzene at the different levels of solvent concentration (Fig. 

5) and gas chromatograms from all the other benzenes at the concentrated level of 450 times (Fig. 6). The 

high scales of Figure 5 and Figure 6 are adjusted at 1000 and 100 mV, respectively.

Numerous peaks appear between 7 and 12 minutes on the gas chromatogram of the 

B411-4 benzene at the 450 times level of solvent concentration (Fig. 5d). These peaks, and also other 

peaks from 12 to 25 minutes retention time, become much more prominent at the 100 mV response level 

(Fig. 6f). The lack of change in the peak patterns at the different levels of solvent concentration 

demonstrates that these peaks are contaminant compounds in the B411-4 benzene. The peak patterns and 

contaminant concentration levels are markedly different among the various benzenes (Figs. 6a to 6f), with 

some benzenes having very high concentrations of contaminant peaks. Moreover, the molecular-weight 

distribution of the contaminants also varies greatly between the different benzenes. For example, JT9154-5 

(Fig. 6a) has significant levels of contaminant peaks over the entire molecular-weight range. On the other 

hand, the EM-BX0212-1 benzene has a more moderate concentration of lower-molecular weight material

14
5 a

B411-4

x10

High Scale 1000mV

5b

B411-4

x20

High Scale 1000mV

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

10 20 30 40 5

ELUTION TIME IN MI

Figure 5. Gas chromatograms at an attenuation of 1000 mV demonstrating contamination in Fisher Scientific 

progressively concentrated by increasing solvent evaporation.
Sa

JT9154-5

x450

High Scale 100mV

<* c

Se

EM-8X0212-1

x450

S High Scale 100mV 

V

Sb

JT9256-3

x450

High Scale 100mV

sr

8411-4

x4SO

High Scale 100mV

Sc

33291

x450

High Scale 100mV

6g

EM-8X0212-1

Once-Oistilled

x4SO

High Scale 100mV

6d

27070

x4SO

High Scale 100mV

6h

EM-BX0212-1

Twice-Olstilled

x4SO

High Scale 100mV

20 30 40 50 60 

ELUT1ON TIME IN MINUTES

70 10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 6. Gas chromatograms at an attenuation of 100 mV of six different benzenes at our maximum level 

of evaporation (x 450, 6a to 6f); and of once-distilled (6g) and twice-distilled (6h) EM-BX0212-1 

benzene, also at our maximum level of evaporation.

16
(Fig. 6e). Moreover, the concentration of this lower-molecular weight material strongly decreases with 

increasing molecular weight, largely disappearing at a retention time of 20 minutes. Concurrently, the EMBX0212-1 benzene also has high concentrations of what appear to be 23 to 31 n-paraffins centered 

around 50 minutes retention time (Fig. 6e). These 23 to C3 i n-paraffins were so identified by retention 

time comparison with the saturated-HC gas chromatogram of Figure Ig. These n-paraffins most probably 

have resulted from wax contamination. The concentration of contaminants in the different benzenes 

decreases in the order of 27070 > JT9154-4 > 33291 > B411-4 > EM-BX0212-1 > JT9256-3. JT9256-3 

is clearly the highest quality benzene and would be sufficient for our study. In fact, the JT9256-3 benzene 

was in use in our laboratory, before this large contamination-check study was carried out, for the analysis 

of the samples reported in Price et al. (1998a and b). However, after using almost all our remaining store 

of this benzene, we attempted to order more, only to find that the J. T. Baker Company had discontinued 

retailing any benzene products. Thus, we attempted to purify the EM-BX0212 benzene by distillation. 

However, the once-distilled EM-BX0212-1 benzene still had concentrations of contaminant peaks too high 

to be ignored (Fig. 6g), although the concentration of these contaminant peaks significantly decreased from 

that of the original EM-BX0212-1 benzene (Fig. 6e). Twice-distilled EM-BX0212-1 benzene (Fig. 6h) has 

even lower concentrations of contaminants than the JT9256-3 benzene (Fig. 6b). Thus, twice-distilled EMBX0212-1 benzene clearly is adequate to be used as a solvent in our research program.

4.14 Benzene/Methanol

Five ml of a 1:1 benzene/methanol solution is used in the column-chromatography fractionseparation step of our procedure to elute the "resin" fraction of the extracted bitumen. Because only one 

half of the 5 ml is condensed to 500 u.1 and possibly subsequently concentrated 15 times for samples with 

low concentrations of indigenous organic compounds, the maximum contaminant concentration in the 

condensed benzene/methanol would be 75 times. Thus, in this step of our examination of solvent 

contamination, the benzene-methanol solution was concentrated 75 times and the contaminant 

concentrations were then analyzed.

Five ml of benzene/methanol was placed in a beaker and passively evaporated to 1 ml. Three 

hundred u.1 of this benzene/methanol solution was then evaporated to 20 u.1 and analyzed by FID gas 

chromatography. We checked two benzene/methanol solutions which were 1:1 mixtures of twice-distilled 

EM-BX0212-1 benzene and A452-4 (HPLC by Fisher Scientific) methanol or A454-4 (OPTIMA by Fisher 

Scientific) methanol. The two gas chromatograms from these mixtures, concentrated 75 times, are shown 

in Figure 7. The high scales of Figure 7 are adjusted to 100 mV.

There are several peaks before the 10 minute elution time on the gas chromatogram of the EMBX0212-1 twiced-distilled benzene and A452-4 methanol 1:1 mixture (Fig. 7a); however, these peak 

heights are low. The A454-4 1:1 benzene/methanol mixture has an extremely low contaminant 

concentration (Fig. 7b), and thus this mixture is sufficiently pure to be used as an organic solvent in our 

research program.

17
7a

1:1 Benzene-Methanol

(A452-4 methanol)

x75

High Scale 100mV

7b

1:1 Benzene-Methanol

(A454-4 methanol)

x75

High Scale 100mV

20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 7. Gas chromatograms of 1:1 benzene-methanol mixtures using twice-distilled EM-BX0212-1 

benzene and two different methanols, at our maximum level of evaporation (x75).

18
4.2 APPARATUS

4.21 Glassware

We bake most of our glassware (pipettes and collection vials for the column chromatography, vials 

and beakers used for evaporation, the thimble and flask of the Soxhlet-extraction assembly, etc.) at 450°C 

for 12 hours before use. Glassware which can not be baked because of size or fragility concerns (for 

example the Soxhlet extraction thimble holder and condenser) are thoroughly rinsed three times with 

dichloromethane (once-distilled D150-4).

The approach of baking glassware at 400°-450°C is commonly used in organic geochemistry, 

especially in the study of organic compounds thought to be indigenous in meteorites, to avoid organic 

contamination from laboratory procedures. Previous unpublished studies within our laboratory have 

demonstrated that this method completely eliminates organic contamination. A check carried out in our 

laboratory (discussed below) reconfirmed this conclusion.

4.22 Cone-Vial Cap

Samples ready for gas-chromatographic analysis are placed in 300 ul cone vials which are sealed 

with aluminum caps crimped over Teflon-coated silicone-based septa. Although Teflon and silicone-based 

septa are thought to be stable in exposure to most organic solvents, the possibility of contamination from 

the vial cap was nonetheless checked.

Three of the solvents we use (twice-distilled H303-4 hexane, twice-distilled EM-BX0212-1 

benzene, and once-distilled D150-4 dichloromethane) were placed in three cone vials and capped. The 

capped vials sat sealed for two days and were then analyzed by FID gas chromatograpyhy (Fig. 8). The 

high scales of the three Figure 8 chromatograms are to 100 mV.

The three-Figure 8 gas chromatograms have no contaminant peaks except for a very small toluene 

peak (from the benzene solvent) in the Figure 8b benzene-leach chromatogram. Thus, the cone-vial septa 

can be used to seal our samples for analysis with no fear of contamination.

4.23 Rubber Bulb

We use disposable 1-2 ml transfer pipettes with rubber bulbs to transfer many of the liquids 

(organic solvents and extracts from samples) generated in our research study. Although we always keep 

those liquids from contacting the rubber bulbs, we cannot exclude a future possible accident in which 

solvents may contact the rubber bulbs. In such a case, we must know the characteristics of the materials 

dissolved from the rubber bulb, in order to differentiate those materials from indigenous organic 

compounds extracted from a rock sample. Thus, the rubber bulb was rinsed with dichloromethane (once 

distilled D150-4), which is the strongest and most polar solvent used in our research. After replacement of 

the dichloromethane in the bulb rinse with hexane (twice distilled H303-4), the replaced rinse was analyzed 

by FID gas chromatography. The resulting chromatogram is shown in Figure 9. Similar rinses of the 

transfer-pipette rubber bulbs were also carried out with our twice-distilled hexane and benzene. Similar 

results were obtained although the peak distributions were different depending on the solvent. Moreover, 

the amount of leached material decreased in the order: dichloromethane > benzene > hexane.

19
8a

Sealed Cone Vial

H303-4 Hexane

(Twice-Distilled)

High Scale 100mV

8b

Sealed Cone Vial

EM-BX0212-1 Benzene

(Twice-Distilled)

High Scale 100mV

8c

Sealed Cone Vial

D150-4 Dichloromethane

(Once-Distilled)

High Scale 100mV

10 20 30 40 50 60 70 

ELUTION TIME IN MINUTES

Figure 8. Gas chromatograms of three different solvents sealed in our auto sampler cone vials for tvvo days 

with Teflon-backed septa.

20
The gas chromatogram from the rubber bulb rinse has seven principal peaks between 35 to 60 

minutes retention time (Fig. 9) with some smaller peaks over 12 to 75 minutes retention time. If some 

solvent and/or sample had ever come in contact with the rubber bulb when transferring our solvent samples 

by pipette, then the transferred materials would contain organic compounds with peak patterns similar to 

that in Figure 9 (or similar to the hexane or benzene leaches). However, we never allowed solvent to 

contact the transfer-pipettes rubber bulb nor did we detect contamination from rubber bulbs in any of our 

samples.

4.24 Copper Strip

An activated copper strip, or as many as five strips in some cases, is/are used in the round- bottom 

flask of the Soxhlet extraction apparatus with the dichloromethane to remove free sulfur from the extract. 

(Free sulfur in the extract prevents correct measurement of the sample weight). Although one would 

suspect that organic contamination would be nonexistent, the strips were nonetheless checked as part of the 

overall contamination check.

Twenty-five new copper strips (15 x 75 mm) were activated by soaking them in hydrochloric acid 

(3N), immediately turning the color of the strips from copper to salmon-pink. The strips were then washed 

with tap water followed by methanol (A454-4), and then stored in a beaker with enough dichloromethane 

(once distilled D150-4) to cover the copper strips for 10 days. The dichloromethane was concentrated and 

analyzed by FID gas chromatography, the resulting gas chromatogram shown in Figure lOa. The copper 

strips were then reactivated in hydrochloric acid and treated again in the manner described above, except 

that they each were rinsed by dichloromethane before the dichloromethane soak. The second resulting gas 

chromatogram is shown in Figure lOb.

The extract obtained from 25 activated new copper strips contains high concentrations of normal 

alkanes ranging from Q9 to 37, with a maximum at C2s (Fig. lOa). On the other hand, the rinse from the 

original 25 copper strips after reactivation with hydrochloric acid following the original 10-day 

dichloromethane soak (and then soaked again in dichloromethane), does not contain detectable organic 

compounds (Fig. lOb). These two experiments demonstrate that although new copper strips are coated 

with wax, this wax is a surficial coating which can be rinsed off with organic solvents. High boiling waxy 

compounds are often found on the surfaces of new-rolled or machined metal products (1968 personal 

communication to Leigh Price from Robert Rex, then Professor of Geology, University of California at 

Riverside). Thus, rinsing the copper strips (whether new or used) before use prevents contamination from 

this source. These experiments also demonstrate that activated copper strips do not react with 

dichloromethane to produce organic contaminants. As long as we rinse these copper strips using 

dichloromethane before the use, we do not need to be concerned with possible contamination from activated 

copper strips.

4.25 Alumina / Silica-Gel Column

An alumina/silica-gel column is used in our procedure for fraction-separation chromatography. 

Alumina and silica gel may have absorbed organic materials during their manufacturing and/or packaging 

processes, because, after all, they are absorbents. It is thus important to determine the possible level of 

such contamination by performing a blank column separation in a manner which duplicates that used in our 

study of rock samples.

21
9a

Rubber Bulb Rinse

H303-4 Hexane

(Twice-Distilled)

High Scale 78mV

9b

Rubber Bulb Rinse

EM-BX0212-1 Benzene

(Twice-Distilled)

High Scale 85mV

9c

Rubber Bulb Rinse

D150-4 Oichloromethane

(Once-Distilled)

High Scale 87mV

j

10 20 30 40 50 60 70 

ELUTION TIME IN MINUTES

Figure 9. Gas chromatograms of rinses (using three different solvents) of the rubber transfer pipette bulbs 

used in our procedure.

22
tf)

CN, 

CJCN

10a <£ c

New Activated £

Copper Strips

High Scale 433mV

4u, .. -i.-i ,

C

CN

CJ

C.

CN

CJ i

C.

0

CJ

C 

^ r "'-'I '

> » 

1 ^~

^^cn

t: o

0

CO

CJ

1 c,-

n 

0

c.

jjjbb

CN

n

CJ

C n 52

^

n X

u i 9'

C 3 i«,

CJ n

c/9

c.

1' 1 i

p»** ..JliujJjJL^

 r I 

10b

Used Re-Activated 

Copper Strips 

High Scale 100mV

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 10. Gas chromatograms of a dichloromethane rinse of new activated copper strips (10a) and of used 

(previously rinsed) copper strips (lOb).

23
The alumina/silica-gel column consists of fine silica gel (mesh size from 100 to 200, No. 923 by 

DAVISON CHEMICAL); coarse silica gel (mesh size from 60 to 100, No. 62 by DAVISON 

CHEMICAL); and aluminum oxide (BAKER ANALYZED reagent by J. T. Baker). Our first experiments 

with blank columns revealed that significant concentrations of contaminant peaks could be present in our 

saturated- and aromatic-HC and resin fractions which were eluted from the blank columns; however, gas 

chromatograms of those analyses will not be shown here. Thus, the absorbents appeared to be badly 

contaminated. Soxhlet extraction of the absorbents revealed this to be the case, as the solvent in the roundbottom (boiling) flask of the Soxhlet apparatus was colored bright yellow after extraction of the 

absorbents. As such, we elected to clean the absorbents by baking them at 400°C for 24 hours. The baked 

absorbents were then put in a dessicator with water for 10 days, such that they were completely 

deactivated. The three absorbents were then reactivated by baking them at 240°C for 24 hours. After 

packing silica glass wool (baked at 400°C for 24 hours) and a small cut piece of a GF/A silica-fiber filter 

into a disposable serological pipette (5 ml), 3 ml of a 923 silica-gel slurry of hexane (twice-distilled H303- 

4) is added to the pipette, 2 ml of 62 silica-gel slurry to is added, followed by 1 ml of alumina slurry. 

Three fractions are obtained in the order of: saturated HCS, aromatic HCS, and lastly resins. The 

saturated-HC fraction is collected by eluting it with 15 ml of twice-distilled H303-4 hexane, followed by 

initiating the benzene elution (20 ml of twice-distilled EM-BX0212-1 benzene). When the aromatic-HC 

elution front is 1.5 ml from the bottom of the column, the collection vial for the saturated HCS is removed 

and replaced by the collection vial for the aromatic HCS. After the 20 ml of benzene pass through the 

column, 5 ml of 1:1 benzene-methanol (twice-distilled EM-BX0212-1 benzene; A454-4 methanol) is added 

to the column, to commence the elution of the resins. When the resin elution front is 1.5 ml from the 

bottom of the column, the aromatic-HC collection vial is removed and replaced by the resin collection vial.

We performed the fraction-separation procedure described above, but using a blank silicagel/alumina column wherein the absorbents had previously been baked at 400°C for 24 hours, as described 

above. The three collected fractions (saturated HCS, aromatic HCS, and resins) were all condensed by 

passive evaporation to 66 uL, which is the maximum solvent concentration level for the three fractions in 

our study. The three fractions were then analyzed by FID gas chromatography (Fig. 11). To compare the 

Figure 11 chromatograms with those from a rock sample (discussed below), the high scales of all three 

chromatograms were adjusted to 100 mv.

The gas chromatogram of the saturated-HC fraction (Fig. 1 la) separated by the alumina/silica-gel 

column has no peaks except for a few small peaks on the tail of the solvent peak. The aromatic-HC 

fraction from the column chromatography has several minor peaks ranging from 6.5 to 17 minutes of 

retention time (Fig. lib). From retention times using aromatic HC standards (see Price et al, 1998; or 

Price and Le Fever, 1994), peak Bl is most likely toluene; peak B2 ethylbenzene; peak B3 para and meta 

xylene; peak B4 orthoxylene; peak B5 1,2,4- and, 1,3,4-trimethylbenzene. Peak B6 is unidentified.

Note that the Bl to B6 peaks of Figure 1 Ib are the same peaks as in Figure 6h, albeit larger. This 

suggests that these minor amounts of contaminant peaks have originated from the solvent, and that our 

second benzene distillation in the case of the Figure 1 Ib solvent, was less efficient than in the case of the 

Figure 6h solvent. We have since rectified this problem by decreasing the distillation rate for the second 

benzene distillation.

24
Column Blank 

Saturated HCS 

High Scale 100mV

Column Blank 

Aromatic HCS 

High Scale 100mV

\\ H

11C

Column Blank

Resins

High Scale 100mV

20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 11. Gas chromatogram of the saturated HCS (1 la), aromatic HCS (1 Ib) and resins (lie) from a 

blank column elution. Chromatogram labeling explained in text.

25
The resin fraction eluted by the column chromatography has a prominent peak at a retention time 

of 22 minutes (peak "Ml5"), and a number of smaller peaks ranging from 7 to 18 minutes (Fig. lie). The 

lowest-boiling compounds of Figure 1 Ic (11 minutes and less) elute over the same retention times as the 

low-boiling peaks of Figure 7b. Thus, we attribute the peaks in 1 Ic to less pure original methanol than that 

used in Figure 7b. (These two methanols had different manufacturer lot numbers). We have circumvented 

this problem by checking the purity of all new lots of methanol (and all other solvents we use). If the purity 

of new methanol is unsatisfactory, then we distill it once.

We now purchase all solvents, especially dichloromethane, in large quantities of single 

manufacturers lots, and analyze a sample of that lot for purity. If the solvent is found to be impure, the 

entire lot is returned and exchanged for another one. We have found that even with a single manufacturer's 

grade and type of solvent, there can be a substantial variation in original purity between different lots. To 

avoid solvent contamination contributions to our sample extracts, we have found that solvent purity must 

be constantly monitored.

The large peak in Figure 1 Ic at 22 minutes retention time (peak Ml5) originates from the column 

chromatography procedure, because the peak never appears in any of the checks on solvent purity. 

However, in spite of repeated attempts along different lines, to isolate the cause for the origin of this peak, 

we were only able to identify its origin late in the study: from the 5 ml serological pipettes used for fraction 

separation by column chromatography. When these pipettes were baked at 450°C, the painted ml 

gradations on the pipettes flaked off. Since these gradations were necessary during several steps of both 

preparation of the columns and for the actual column chromatography, we elected to clean the columns by 

rinsing them with solvent rather than baking them. However, we used hexane as the rinse solvent, and 

hexane was not removing the contaminant responsible for the M15 peak from the inside of the serological 

pipettes. Late in the study, we began rinsing the serological pipettes with 1:1 benzene methanol, which did 

remove the contaminant causing the M15 peak in the resin gas chromatograms. Although we had been 

rinsing all other glassware, which was not baked at 450°, with dichloromethane, this experience drove 

home the necessity of rinsing unbaked glassware with a polar solvent.

Aside from the Ml 5 peak in the resin fraction, none of the Figure 11 chromatograms have 

substantial contaminant peaks. The small low-boiling peaks that are present in Figures 1 Ib and 1 Ic have 

been further rninirnized by careful monitoring of original solvent purity and running our distillation units at 

lower distillation rates. Thus, for our research purposes, the fraction-separation column-chromatography 

procedure we use is more than adequate for our needs. We further discuss the labeled peaks Bl to B6 (Fig. 

1 Ib) and Ml to M15 (Fig. 1 Ic) below.

4.26 Cardboard Storage Cartons

We normally store all our rock samples to be studied (either broken into large chunks or powdered 

to minus 100 or 200 mesh) into pre-baked glass jars with foil-lined lids. However, at one point early in our 

joint research project, we ran out of large glass jars and temporarily stored some crushed (but not 

powdered) samples in cylindrical white cardboard cartons ("Paper Cans" by FOND A). Gas 

chromatograms of these samples were substantially different than and obviously contaminated compared to 

those from other samples of the same set. The gas chromatograms in question contained a set of highboiling waxes in the saturated HCS and other waxy appearing compounds in the aromatic HC and resin 

fractions. We isolated the source of contamination in these samples to a wax coating on the inside of 

cardboard cartons. Our early experience in this matter alerted us to the insidious nature of possible organic

26
contamination to our samples, in all steps of our analytical procedure, from sample collection to final gas 

chromatographic or mass spectrometric analysis. We here present the qualitative data from our "papercarton experience" to illustrate possible problems which may arise in analyses of crystalline rocks which 

bear low quantities of indigenous organic compounds.

Once we noticed the contamination in the above-referenced samples, and isolated the source as 

possibly the wax coating on the FOND A cardboard storage cartons, we obtained an "extract" of these 

cartons by rinsing the inside of a carton with dichloromethane (once distilled D150-4). After the 

dichloromethane of the extract was replaced with hexane (twice distilled H303-4), the extract was 

separated into three fractions by alumina/silica-gel fraction-separation column chromatography. Gas 

chromatograms of the three fractions from FID gas chromatography are shown in Figure 12, along with 

gas chromatograms of the three fractions (saturated and aromatic HCS, and resins) from a badly cartoncontaminated sample.

The gas chromatogram from the saturated-HC fraction of the carton rinse (Fig. 12a) contains n-Ci9 

to n-Css alkanes, with a maximum at the 24 n-paraffin. In other words, high concentrations of wax. The 

gas chromatogram of the aromatic HCS from the carton rinse (Fig. 12b) contains multiple families of 

periodic series of compounds: counting doublets, four different series with prominent peaks, and perhaps six 

more separate series with much smaller peak heights. We hypothesize that all these peaks in the aromatic 

HC fraction represent different homologous series of double-bond bearing aliphatic HCS, with the double 

bond, or double bonds, in different carbon positions for each series. However, no attempt was made to 

identify the compounds responsible for these different peaks. The gas chromatograms of the resin fraction 

from the carton rinse (Fig. 12c) contains perhaps three series of homologous periodic peaks, plus a large 

complex of peaks at 45 minutes retention time. The large peak at 22 minutes is the previously-identified 

contaminant peak (M-15, Fig. lie) which originates from fraction-separation column chromatography. We 

have not tried to identify the compounds responsible for the different series of periodically-repeating peaks 

in Figure 12c. However, we suspect that they may be different series of aliphatic HCS with carboxylic acid 

or ester bonds, or alcohols, or aldehydes, all with or without double bonds. The ratio of the saturated and 

aromatic HCS, and resins obtained from the carton rinse by weight is 70:1:14, respectively. Thus, the 

principal components of the contamination from the carton are 21 to C3o n-paraffins.

Gas chromatograms from one of the most badly-contaminated samples (AS-607, a metamorphic rock from 

Sanbagawa, Japan) from the FOND A cartons are shown in Figure 12d to 12f, with the saturated HCS 

shown in Figure 12d at lOOmV. To keep the largest peak in Figure 12d on of indigenous saturated HCS 

cannot be seen. Thus, the vertical scale of Figure 12d was substantially attenuated to lOOmV. As is 

apparent, the low concentrations of indigenous saturated HCS in the AS-607 sample (Fig. 12d) are 

absolutely dwarfed by the wax contamination from the cardboard carton in which the crushed chips (-1/2", 

1.27cm) of this rock were stored after crushing and before powdering. We know that the HCS marked 

indigenous in Figure 12d are just that, for two reasons: First, vertical expansion of the Figure 12a 

chromatogram, which is only the contaminating wax, to lOOmV, does not reveal significant concentrations 

of n-Ci9- paraffins. Second, analyses of Sanbagawa samples not contaminated by wax demonstrates 

saturated-HC distributions similar to those labeled indigenous in Figure 12d.

Figure 12e shows the wax-contaminated aromatic HCS extracted from the AS-607 sample. There 

is also a significant amount of contamination in the aromatic HCS; however, the relative level of 

contamination is much less than that of the saturated HCS (Fig. 12d). This is because, as stated above, the 

wax contamination is composed of 82.2% saturated HCS and only 1.2% aromatic HCS (with the resins 

making up the balance (16.6%) of the wax contamination).

27
12a

Carton Rinse 

Saturated HCS 

High Scale 407mV

u

CO

o,.

12d

AS-607

Wax-Contaminated 

Saturated HCS 

High Scale 100mV

12b

Carton Rinse 

Aromatic HCS 

High Scale 154mV

1 Lj=

12e

AS-607

Wax-Contaminated 

Aromatic HCS 

High Scale 360mV

UJJL 1 ..J

12c

Carton Rinse

Resins

High Scale 416mV

12f

AS-607

Wax-Contaminated

Resins

High Scale 100mV

o u

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70 10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 12. Gas chromatograms of the saturated HCS (12a) aromatic HCS (12b), and resins (12c) from a 

dichloromethane rinse of the wax-coated interior of a FOND A paper carton. Gas chromatograms 

from a sample contaminated by such a paper carbon are shown in 12d (saturated HCS), 12e 

(aromatic HCS), and 12f (resins). n-C and a number refers to the respective n-paraffin in 12a and 

12d. PRI is pristane and PHY is phytane in 12d. "C" in 12f refers to contaminant peaks in the 

resin fraction from the AS-607 sample. All other peaks in the 12f chromatogram are indigenous to 

the sample.

28
The relative amount of wax contamination in the resin fraction (Fig. 12f) is even lower than that in 

the aromatic HCS (Fig. 12e), with the contaminant peaks labeled as "C" in Figure 12f. The reason for the 

even greater relative (apparent) decrease of contaminant peaks in the resin fraction is that, as discussed in 

Price et al. (1998, 1999), the resin fraction in carbonaceous high-rank rocks is the largest of the three 

fractions (by weight) resulting from column chromatography. In contrast, the aromatic-HC fraction is the 

smallest. The reasons for these observations are discussed in Price et al. (1988, 1999) and will not be 

detailed here.

The point of this discussion about contamination from the FOND A cardboard cartons is to 

demonstrate the magnitude of contamination possible, from a seemingly inconsequential step, in 

the analysis of extractable organic compounds which can be present in low concentrations in high-rank 

crystalline rocks. High levels of attention must be constantly focused to avoid significant contamination in 

the analysis of such samples.

4.27 Rock Crushing and Powdering

After thoroughly cleaning the rock surfaces, all rock samples must be crushed and ground to a 

powder (either to 100 mesh and less or to 200 mesh and less). Crushing is carried out via a large jaw 

crusher to a 1/2 inch (1.22 cm) size and less. Rocks are then powdered via steel ball mills. Both 

apparatuses are thoroughly cleaned before our use: The jaw crusher is wetted with water, scrubbed with a 

wire brush, rinsed with water and then rinsed with once-distilled D150-4 dichloromethane. The ball mills 

are cleaned by blowing them out with air, powdering a commercial-grade beach sand in them, blowing the 

powder out with compressed air, and then rinsing the mill cylinder and balls with the dichloromethane.

We hypothesized that the large contaminant peak in the resin fraction at 22.0 minutes (peak M15, 

Fig. lie) may have originated from the rock-grinding process, and thus resolved to address the matter. 

Moreover, every step of the complete analytical process, including rock crushing and powdering, had to be 

checked as a possible contributor to analytically-derived contamination. This check was accomplished by 

subjecting a rock thought to be devoid of extractable-organic compounds (a sample blank) to every step of 

our analytical process, including crushing and grinding.

»

4.271 Vein ("Buin Quartz

Vein ("bull") quartz (origin unknown), used as a xeriscape decorator rock outside our laboratory at 

the Denver Federal Center was originally chosen to be used as the sample blank. The rock was cleaned 

under running water, air dried, rinsed with once-distilled D150-4 dichloromethane, and then put through the 

jaw crusher, and finally ground to 100 mesh and less in our ball mills. The powdered bull quartz was then 

baked at 700°C for 5 days, and 500 grams of the baked quartz was Soxhlet extracted for 10 days. The 

resulting extract was subjected to our complete analytical workup, including fraction-separation column 

chromatography. The three fractions were then analyzed by gas chromatography. The gas chromatogram 

of the saturated-HC fraction is shown in Figure 13 a. Solvent contamination is present from about 8 to 10 

minutes. However, a series of small n-paraffin peaks (some of which are labeled with their carbon number) 

are also present from 35 to 55 minutes. The concentration level of these n-paraffins is much less than that 

found in even our leanest samples, thus the presence of these peaks was not of great concern to us. On the 

other hand, we were curious as to their point of origin.

Gas chromatograms of the aromatic-HC and resin fractions are shown in Figures 13b and 13c, 

respectively. Again the early-eluting peaks (at and before 10 minutes) in both chromatograms are due to

29
13a

Baked Bull Quartz 

700°C / Sdays 

Saturated HCS 

High Scale 40mV

13b

Baked Bull Quartz 

700°C / Sdays 

Aromatic HCS 

High Scale 44mV

13c

Baked Bull Quartz

700°C / Sdays

Resins

High Scale 100mV

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 13. Gas chromatograms of the saturated HCS (13a), aromatic HCS (13b), and resins (13c) 

extracted from bull quartz. n-C and a number refers to the respective n-paraffin in 13 a. 

"COL" in the saturated-HC (13a) and resin (13c) chromatograms is a contaminant peak from the 

gas chromatograph column. M15 is a contaminant from the seriological pipettes.

30
low-boiling contaminants in the solvents. However, there are still other numerous small peaks up to a 55 

minute elution time in the aromatic-HC gas chromatogram, and up to about 63 minutes in the resin gas 

chromatogram. In both cases, the concentration levels of the contaminants were not high enough to be of 

major concern to us. However, again, in both cases, the origin of both sets of contaminant peaks was of 

interest to us. Note that the highest contaminant levels in the Figure 13 gas chromatograms was in the resin 

fraction (Fig. 13c).

4.272 Flint-Glass Bottle

As to the origin of the compounds in Figure 13, we hypothesized that they had not originated from 

the analytical procedure but instead may have been from fluid inclusions which may have been present in the 

bull quartz. To check this possibility, we elected to use flint-glass quart bottles as sample blanks. The 

bottles were cleaned, baked at 450°C for 5 days, crushed and powdered to 100 mesh and less, and subjected 

to the same analytical workup as the bull quartz. The saturated-HC gas chromatogram (Fig. 14a), to our 

surprise, still had noticeable, albeit small, concentrations of Ci4 to 24 n-paraffins and isoprenoid HCS. The 

concentrations of the aromatic HCS from 45 to 55 minutes noticeably decreased (Fig. 14b) compared to the 

bull quartz aromatic-HC gas chromatogram (Fig. 13b). The concentration of the resin peaks eluting after 

20 minutes also decreased slightly in the case of the ground flint-glass bottle compared to the bull quartz 

(Fig. 14c versus Fig. 13c, respectively).

As it turned out, the n-paraffin contaminant peaks of Figures 13a and 14a were largely, and perhaps 

wholly, from copper-strip wax contamination. It was only later in our research, after we had-made checks 

on the copper strips, that we realized we had put multiple new copper strips, of a different manufactured lot 

than that responsible for Figure lOa, in the round-bottom-extraction flasks for the bull-quartz and flint-glass 

extractions. Thus, most, if not all, of the contamination from our two sample "blanks" (bull quartz and flint 

glass) was from new copper strips.

However, there still is the possibility of other sources of contamination: Recall the differences in the 

aromatic HCS between the bull quartz (Fig. 13b) and flint glass (Fig. 14b) samples over 43 to 54 minutes. 

It is possible that these differences were due to the fact that copper strips from different manufacturers' lots 

were put in the bull quartz and flint glass round-bottom boiling flasks. However, careful perusal of the resin 

gas chromatograms (Fig. 13c and 14c) for these two samples reveals more significant differences in peak 

distribution. Moreover, the bull quartz sample has a slightly greater resin concentration than the flint-glass 

sample. This result would be expected if there were low concentrations of naturally-occurring indigenous 

extractable organic compounds in the vein bull quartz (Price et al. 1998 and 1999). Given the results of 

Price et al. (1998 and 1999), and other investigators (reviewed in Price et al. 1998 and 1999), as well as 

our (yet unpublished) results regarding the analyses of many different types of high-rank crystalline rocks, 

the presence of small concentrations of extractable-organic compounds in hydrothermally-deposited vein 

quartz would be expected. Thus, we conclude that very small concentrations of organic compounds may be 

present in fluid inclusions in the vein quartz. After heating the vein quartz at 700°C, some fraction of those 

inclusions which did not rupture during the heating might fracture on thermal contraction, thus exposing the 

inclusions, and the possible organic compounds therein to Soxhlet extraction.

31
14a

Baked Flint Glass 

450°C / Sdays 

Saturated HCS 

High Scale 44mV

14b

Baked Flint Glass 

450°C / Sdays 

Aromatic HCS 

High Scale 47mV

14c

Baked Flint Glass

450°C / Sdays

Resins

High Scale 100mV

20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 14. Gas chromatograms of the saturated HCS (Fig. 14a), aromatic HCS (14b), and resins (14c)

extracted from a sample blank from a flint-glass bottle sample blank. "COL" in the saturated-HC 

(14a) and resin chromatograms (14c) is a contaminant peak from the gas chromatograph column; 

M-15 is a recurring contaminant peak from the seriological pipettes. n-C and a number refers to 

the respective n-paraffins in 14a.

32
4.273 Source-Rock Heating

One may argue that heating the quartz at 700°C for 5 days in an oxygen-rich atmosphere would 

have completely thermally destroyed any organic compounds present in the rock. This is not the case. We 

heated 500 grams of 60 mesh and smaller lower Cretaceous immature source rock previously used as a 

standard for ROCK-EVAL analysis in our laboratory at 500°C for 5 days in an oven open to the 

atmosphere. This shale has a total organic carbon (TOC) content of 4% and ROCK-EVAL hydrogen 

indices of around 400. After baking the source rock, it was powdered to 100 mesh and less and then Soxhlet 

extracted. Given the severity of the heating conditions and by all that is sacred in petroleum-geochemistry, 

all extractable-organic compounds should have been thermally destroyed. This was not the case (Fig. 15). 

In Figure 15, gas chromatograms are presented at both high and low mV settings. The saturated HCS are 

shown in Figures 15a and d, the aromatic HCS in Figures 15b and e, and the resins in Figures 15c and f. As 

is evident in the chromatograms of Figure 15, relatively large amounts of lower-molecular weight 

extractable material remain in the source rock, in spite of the severe heating conditions.

There clearly has been significant thermal decomposition of the extractable HCS in this rock as is 

demonstrated by the dominance of lower-molecular weight material in all three chromatograms. Moreover, 

the thermal destruction reactions have resulted in distributions typical of thermal cracking from laboratory 

experiments (Price, 1993). Also, only small concentrations of C\$+ material remained in the rock after 

baking as determined by weighing splits of the fractions obtained from column chromatography, to wit: 

saturated HCS, 0.478 ppm; aromatic HCS 0.132 ppm, and resins, 0.106 ppm. Be all that as it may, we 

clearly cannot assume that heating the bull-quartz at 700°C for 5 days would destroy all extractable-organic 

compounds in the closed-system, water-wet fluid inclusions of the quartz, if such compounds and inclusions 

were present.

4.28 The Cleaning Sand

Another source of contamination that could influence the procedural blanks (bull quartz, flint glass 

bottles), would be the sand used to clean the ball mill before (and after) powdering our rocks. With this in 

mind, we carried out three experiments: First, we powdered previously-crushed and baked (450°C for 5 

days) flint-glass bottles in a ball mill that had been cleaned with the sand and then rinsed with 

dichloromethane. Second, we powdered splits of the same crushed and baked flint-glass bottles in a ball mill 

which had had multiple cleanings with the sand during the powdering of the flint-glass bottles, and no 

dichloromethane rinses. Third, we powdered 500 grams of the beach sand to 100 mesh and less.

Five hundred grams of powder from each of the above were Soxhlet extracted and subjected to our 

full analytical workup, including column chromatography. The saturated- and aromatic-HC, and resin gas 

chromatograms from these three samples are shown in Figure 16. Unfortunately, the resin fractions from 

these samples were lost during workup. The six chromatograms of Figure 16 result from a solvent-volume 

reduction of 18,000 fold. Figures 16a, 16b, 16d, and 16e demonstrate that there are no detectable HCS in 

the saturated- and aromatic-HC gas chromatograms for the two flint-glass samples. Figures 16b and 16e 

(multiple sand cleanings, no dichloromethane rinse) would be expected to demonstrate the presence of 

contamination, compared to Figures 16a and 16d (one sand cleaning and a dichloromethane rinse), if there 

were any from the sand. Thus, we may conclude that no detectable contamination within the saturated- and 

aromatic-HC fractions arises from use of the sand to clean the ball mills.

Figures 16c and 16f show saturated- and aromatic-HC gas chromatograrns from the extraction of 

the ground beach sand. Significant amounts (relative to Figs. 16a and 16b) of saturated HCS (Fig. 16c)

33
1Sa

Baked Source Rock 

500°C / Sdays 

Saturated HCS 

High Scale 1000mV

15d

Baked Source Rock 

500°C / Sdays 

Saturated HCS 

High Scale 100mV

15b

Baked Source Rock 

500°C / Sdays 

Aromatic HCS 

High Scale 374mV

15e

Baked Source Rock 

500°C / Sdays 

Aromatic HCS 

High Scale 100mV

15c

Baked Source Rock

500°C / Sdays

Resins

High Scale S15mV

15f

Baked Source Rock

500°C/Sdays

Resins

High Scale SOmV

20 30 40 50 60 

ELUTION TIME IN MINUTES

70 10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 15. Saturated-HC gas chromatograms at two different attenuations (15a, 1000 mV; 15d 100 mV); 

aromatic-HC gas chromatograms at two different attenuations (15b, 374 mV; 15e, 100 mV); and 

resin gas chromatograms at two different attenuations (15c, 615 mV; 15f 50 mV), all from heating 

an organic rich (immature) shale at 500°C for 5 days in an oven open to the atmosphere.

34
16a

Baked Flint Glass 

CH 2 CI 2 Rinse after 

One Sand Cleaning 

Saturated HCS 

High Scale 100mV

16d

Baked Flint Glass 

CH 2CI 2 Rinse after 

One Sand Cleaning 

Aromatic HCS 

High Scale 100mV

16b

Baked Flint Glass

Multiple Sand Cleanings

No CHjClj Rinse

Saturated HCS

High Scale 100mV

16e

Baked Flint Glass

Multiple Sand Cleanings

No CH Z CI 2 Rinse

Aromatic HCS

High Scale 100mV

9'c v= o 

16c

Powdered Beach Sand 

Saturated HCS 

High Scale 100mV

16f

Powdered Beach Sand 

Aromatic HCS 

High Scale lOOmV

UB.

in

<N -

oc

c<-

1

)

) o 

r> 

U

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70 10 20 30 40 50 60 

ELUTION TIME IN MINUTES

Figure 16. Saturated-HC gas chromatograms from flint-glass bottle sample blanks prepared by one sand 

cleaning before powdering the bottle with a dichloromethane rinse (16a), and by multiple sand 

cleanings while powdering the bottle, with no dichloromethane rinses (16b); and from an extract of 

the powdered sand used to clean the ball mills (16c). Aromatic-HC gas chromatograms from the 

same sample-blanks and sand are respectively shown by 16d to 16f. n-C and a number refers to 

the respective n-paraffin in 16c.
were present in the sand. However, the absolute amounts are very low, since Fig. 16c represents all the 

saturated HCS obtained from extracting 500 grams of beach sand. Be that as it may, because no sample 

split was taken for C\$+ weights for any of the beach-sand fractions from column chromatography, the 

actual amounts of saturated- and aromatic-HCS obtained from column chromatography are unknown, but 

we estimate that they would be in the range of 0.01 to 0.1 mg, if we were able to weigh them, or 0.02 to 0.2 

ppm by weight.

Small amounts of aromatic HCS were also present in the beach sand (Fig. 16f). Although low 

concentrations of saturated- and aromatic HCS are present in the beach sand, these low concentrations did 

not contribute detectable contamination to our sample procedure. This is because Figures 16c and 16f 

result from extraction of 500 grams of sand, whereas only 10 to 20 grams of sand are used to clean the ball 

mill, and that 10 to 20 grams is disposed of, not extracted. This conclusion is obviously substantiated by 

Figures 16a, 16b, and 16d and 16e, which demonstrate no contamination from the beach sand.

4.29 Procedure Blanks

The saturated- and aromatic-HCS of Figure 16a; 16b, 16d, and 16e serve as contamination checks 

wherein blank (non-HC bearing) samples have been subjected to our full analytical workup. Those 

chromatograms demonstrate that no significant concentrations of organic compounds are introduced into our 

analytical procedure at any step of the total process, from sample-preparation to final analysis. However, 

we found that there could be some variance of the level of the background concentration of lower boiling 

materials dependent on solvent distillation rates. To illustrate this point, we here present the results from 

two other procedural blanks, one of which we also ran to further check the possibility of HC-bearing fluid 

inclusions in the bull quartz.

4.291 Bull Quartz

For the first procedure blank, we baked, cleaned and crushed (to roughly 1/2 inch, 1.27cm) pieces 

of bull quartz at 700°C for 5 days. The quartz was then powdered and 500 grams were then Soxhlet 

extracted (using previously-rinsed, reactivated copper strips) and put through our full analytical workup. 

The resulting gas chromatograms for the saturated and aromatic HCS and resins are shown in Figure 17a 

through 17c, respectively.

Significant solvent peaks (at this low attenuation, 44 mV) are present in the saturated-HC 

chromatogram (Fig. 17a) from 8 to 10 minutes and are labeled D4-D7, D9 and SI. Very small C2oto C2s nparaffin peaks are also present, peaks which we can now attribute to fluid inclusions within the bull quartz. 

The aromatic HC gas chromatogram (Fig. 17b) also has a number of small solvent peaks from 6.5 to 16 

minutes elution time. These peaks have been labeled Dl, D2, B1-B6, and A1-A8. No significant 

contaminant peaks are present after 16 minutes.

A series of low-boiling solvent contamination peaks (M2-M15, labeling from Fig. 1 Ic) are present 

in the bull-quartz resin chromatogram. Very small contaminant peaks are also present between the M15 

peak and "COL" contaminant peaks. The presence of peaks in the resin gas chromatogram Fig. 17c) from 

the bull quartz and not in the aromatic HC gas chromatogram is expected if the contaminant peaks of 

Figures 17a and 17c originated from fluid inclusions in the quartz (Price et al. 1998 and 1999). However, 

the concentration of these compounds is far lower than that of the organic compounds in the high-rank 

crystalline rocks we study, as will be demonstrated in Section 5.0, below. Furthermore, the concentration of

36
17a

Bull Quartz 

700°C / Sdays 

Saturated HCS 

High Scale 44mV

17b

Bull Quartz 

700°C/Sdays 

Aromatic HCS 

High Scale 100mV

17c

Bull Quartz

700°C/Sdays

Resins

High Scale 100mV

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 17. Gas chromatograms of saturated HCS (17a) aromatic HCS (17b), and resins (17c) extracted

from a bull quartz sample blank. N-paraffins are shown by n-C and a number in 17a. Labeling of 

the low molecular weight peaks in all three chromatograms explained in text. Also see Figure 13 

caption.

37
the low boiling compounds in Figures 17a to 17c is also low enough, such that in many of the samples we 

work with, only minor problems would result concerning interpretation of analytical results.

The solvent-derived peaks in the Figure 17 gas chromatograms were labeled as follows: The "D" 

peaks in the saturated-HC gas chromatogram (Fig. 17a) originate as solvent contamination from the oncedistilled D150-4 dichloromethane (Fig. 2f). The SI peak (Fig. 17a) is a newly detected contaminant peak in 

the saturated HCS. The Dl and D2 peaks of Figure 17b originate as solvent contamination from the oncedistilled D150-4 dichloromethane (Fig. 2f). The peaks Bl to B6 (Fig. 17b) originate as solvent 

contamination from the twice-distilled EM-BX0212-1 benzene (Fig. 1 Ib). The peaks Al to A8 (Fig. 17b) 

are newly-detected aromatic HCS which most probably also originate as solvent contamination in the twicedistilled EM-BX0212-1 benzene. The peaks labeled M1-M14 (Fig. 17c) originate from solvent 

contamination (Fig. lie). The origin of the M15 peak (Fig. 17c) is unknown.

4.292 Flint-Glass Bottle

As before, the flint-glass quart bottles were cleaned, baked at 450°C for 5 days, crushed and 

powdered to 100 mesh and less, and subjected to our full analytical workup from Soxhlet extraction to gas 

chromatographic analysis of the resulting fractions, the gas chromatograms of which are shown in Figure 

18, the saturated-HC gas chromatogram being Figure 18a. Five small peaks labeled COL-1 to COL-5 were 

present in all six chromatograms of Figure 18. These peaks originated from contamination from the gaschromatograph column, and not from our analytical work up. The saturated-HC gas chromatogram from 

the flint glass bottle (Fig. 18a) has no contaminant peaks originating from our analytical workup except for 

a very small series of peaks over roughly 27 to 44 minutes elution time.

The aromatic HC gas chromatogram has no contaminant peaks except for a relatively large peak at 

about 11 minutes elution time labeled "Fume Hood Peak" (Fig. 18b). This peak did not originate from our 

analytical workup either, but instead originated from cross-fume hood contamination. On the day we were 

allowing the aromatic HC fractions from the flint-glass bottle extraction, and the resins from a concurrentlyrun column blank, to passively evaporate in our fume hood, there was a chemical spill in a laboratory 

areally-continguous to ours. An odor from the materials used to contain the spill soon permeated the 

hallways. Eventually, we began smelling the odor in our fume hood and we realized this odor was a source 

of possible contamination. However, we elected to leave the 8-dram vials in the fume hood to test the 

possibility of contamination to our samples from these fumes. As is evident from Figures 18b and 18f, these 

fumes did result in contamination to our samples, again illustrating that at the highly-sensitive analytical 

level we are concerned with, contamination can result from the unlikiest of sources. Due to this experience 

(Figs. 18b and f), samples undergoing passive evaporation in our fume hoods are covered when an outside 

odor is detected in our hoods.

The gas chromatogram from the resin fraction of the flint-glass bottle exraction is shown in Figure 

18c. The usual large peak from the gas chromatograph column (COL-47) is present. In addition, there are 

a series of small peaks from 21 to 46 minutes elution time. Of the three fractions from column 

chromatography (saturated and aromatic HCS, and resins), the resin fraction typically has the highest levels 

of contamination. However, the levels of contamination in Figure 18c are undectable in our resin analyses, 

because full scale resin gas chromatograms from our high-rank crystalline rock samples always are in the 

500 to lOOOmV range of attenuation.

38
18a

Flint-Glass Bottle 

450°C / Sdays 

Saturated HCS 

High Scale 100mV

18d

Column Blank 

Saturated HCS 

High Scale 100mV

18b

Flint-Glass Bottle 

450°C/Sdays 

Aromatic HCS 

High Scale 100mV

18e

Column Blank 

Aromatic HCS 

High Scale 100mV

18c

Flint-Glass Bottle

450°C / Sdays

Resins

High Scale 100mV

18f

Column Blank

Resins

High Scale 100mV

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 18. Gas chromatograms of saturated HCS (18a and 18d), aromatic HCS (18b and 18e), and resins 

(18c and 18f) from, respectively, a flint-glass bottle sample blank and blank elutions from a silicagel/alumina column. Labeling of the chromatograms is explained in the text.

39
While analyzing the flint-glass bottle sample blank, column blanks were also run, wherein blank 

saturated-HC, aromatic-HC, and resin fractions were concurrently eluted, from a separate column, while the 

flint-glass bottle sample blank was being fractionated. In this manner, we would be able to assign any 

contamination which arose in the 6 eluted fractions to either the crushing-powdering step or the fractionation 

from column chromatography. The gas chromatograms of the three fractions from the column blank are 

shown in Figures 18d to 18f. No contaminant peaks are present in any of the three chromatograms, aside 

from the five peaks from the gas chromatograph column (peaks "COL-1 to COL-5") in all three 

chromatograms, and the contaminant peak from the fume hood odor ("Fume Hood Peak") in the resin gas 

chromatogram (Fig. 18f). These six peaks are all one-time peaks, which do not appear in other sample 

blanks.

From the lack of contaminant peaks in Figures 18d to 18f, we may conclude that the very minor 

contaminant peaks, over elution times of 27 to 44 minutes, in the saturated-HC gas chromatogram of the 

flint glass bottle (Fig. 18a) arises from the crushing and powdering step, as do the minor contaminant peaks 

in the gas chromatogram of the resin fraction from the flint-glass bottle (Fig. 18c). However, as stated, in 

neither case would the contaminant peaks even be detectable in the crystalline rock samples we analyze with 

even the lowest HC concentrations, as will be demonstrated in Section 5.0.

We stress two other points concerning Figure 18. Note that in the gas chromatograms of both resin 

fractions.(Figs. 18c and 18f) the large contaminant peak at 21 minutes is missing. This peak ("Ml5") was 

present in most of our previous examples, and we were never able to identify its origin.

The peak eventually simply disappeared from our sample blanks (and samples), as in the 

chromatograms of Figure 18, and thus its origin remains a mystery. Secondly, note the absence of low 

molecular weight solvent peaks in all of the six chromatograms of Figure 18, especially compared to the 

chromatograms of Figures 1-17 and 19. We determined late in our contamination study that by reducing 

the distillation rates of the solvents we distilled, we were able to make very pure solvents with very low 

amounts of, or no, low-molecular weight contaminant peaks.

The chromatograms of Figure 18 thus serve as representative examples of the degree of 

contamination introduced by our analytical technique currently in use, e.g., very low amounts of 

analytically-derived contamination.

5.0 MANTLE XENOLITH: An Example from the Natural System

Most of the carbonaceous high-rank crystalline rocks we deal with have total "bitumen" contents on 

the order of 2 to 10 ppm by weight, although some concentrations can be much higher (up to 150 ppm, Price 

et al., 1998, 1999). Conversely, other rocks can have much lower concentrations. For example, the mantle 

xenoliths studied by Sugisaki and Mimura (1994) have total bitumen concentrations around 0.5 ppm. As an 

applied example of our analytical procedure, we present the results of an analysis of a mantle xenolith from 

the Hualalai Volcano, Hawaii, a principally olivine-bearing dunite (Fig. 19, sample HUA-2). The saturated 

HCS were at a concentration of 0.156 ppm in the rock, the aromatic HCS at 0.078 ppm, and the resins at 

0.43 ppm.

The saturated-HC gas chromatogram (Fig. 19a) has a pronounced naphthenic hump with nparaffins, isoprenoid HCS, and other compounds on top of the hump. The HUA-2 saturated-HC gas 

chromatogram replicates those reported by Sugisaki and Mimura (1994) from other mantle xenolith

40
19a 

HUA-2

Saturated HCS 

High Scale 100mV

19b 

HUA-2

Aromatic HCS 

High Scale 100mV

\)

19c

HUA-2

Resins

High Scale 1000mV

10 20 30 40 50 60 

ELUTION TIME IN MINUTES

70

Figure 19. Gas chromatograms of saturated HCS (19a), aromatic HCS (19b), and resins (19c) extracted 

from a mantle xenolith. In 19a, n-paraffins are shown by n-C and their respective carbon number, 

PRI is pristane, PHY is phytane. Peak labeling is explained in the text.

41
samples. The aromatic-HC gas chromatogram (Fig. 19b) has a similar, but lower, hump, with 

numerous peaks on it. The gas chromatogram of the resin fraction (Fig. 19c) has a number of 

prominent peaks, two of which are offscale, and the chromatogram has no hump. Price et al. 

(1998, 1999), and unpublished work subsequent to those papers, have demonstrated that many of 

the peaks in gas chromatograms of the aromatic-HC and resin fractions from high-rank crystalline 

rocks are oxygen-bearing organic compounds. However, that topic will not be discussed in detail 

here.

The Figure 19 gas chromatograms allows four relevant conclusions. First, the distribution of peaks 

in all three chromatograms is much different than those arising from the much smaller concentrations of 

laboratory-induced contamination. Second, the low-boiling contaminant peaks in the saturated- and 

aromatic-HC gas chromatograms are the most prominent non-exogenous peaks. In many other samples of 

high-rank crystalline rocks, high concentrations of indigenous low-molecular weight compounds have often 

dwarfed the low-boiling contaminant peaks in the saturated and aromatic HCS. In fact, an indirect example 

of this is present in Figure 19c (resin gas chromatogram), wherein the low-molecular weight contaminant 

solvent peaks (labeled M-2, M-7, M-13, and M-14) are very small compared to the indigenous compounds 

in the resin fraction. Even the normally prominent M-15 and "COL" contaminant peaks of the resin gas 

chromatograms are smaller than the peaks from the compounds indigenous to the sample, and this is 

especially true for the column ("COL") contaminant peak.

Our third conclusion, is that the indigenous bitumen from the HUA-2 rock sample is in much greater 

concentrations than the higher-boiling small contaminant peaks which may arise from our analytical 

procedure (with the exception of the resin M-15 and "COL" contaminant peaks). Moreover, the Figure 19 

gas chromatograms demonstrate that we could successfully analyze organic compounds present in high-rank 

crystalline rocks at concentration levels even lower than 0.1 to 0.5 ppm. The third conclusion allows our 

fourth, to wit: our analytical procedure is more than adequate for the analysis of very low concentrations of 

organic compounds in high-rank crystalline rocks. Of course, one may argue that the bitumen resulting in 

the Figure 19 gas chromatograms is contamination on or in the rock sample. However, both Sugisaki and 

Mimura (1994) and Price et al. (1998, 1999) have replied to this point, a point which does not concern us 

here.

Several other points should be made concerning the Figure 19 gas chromatograms. We processed 

the HUA-2 dunite before learning that we could lower our distillation rates such that the lowest molecular 

weight solvent peaks were greatly decreased or removed altogether (Fig. 18). However, the lower molecular 

weight contaminant peaks labeled in Figures 19a to 19c do not significantly detract from the results of our 

analysis. Observe that the M-15 contaminant peak (Fig. 19c) was still present in our analytical technique 

when the HUA-2 dunite was analyzed. Lastly, note that the HUA-2 sample represents the low-concentration 

end of the samples we analyze. However, the resin gas chromatogram is at 1000 mV full scale, with the two 

largest peaks still offscale. Thus, the small peaks in the resin fraction created by our analytical method (Fig. 

18c) are undetectable in the resin fractions derived from our samples (Fig. 19c).

We conclude that the two principal points of this paper have been made: 1) to demonstrate that no 

significant levels of contamination are introduced from our laboratory procedures into the bitumen extracted 

from high-rank crystalline rock samples we study; and 2) to point out examples of the numerous possible 

pitfalls in the analysis of such rocks, so that other laboratories may replicate our results concerning the 

study of organic compounds in high-rank crystalline rocks.

42
Acknowledgements

We thank Hao Fang, Mike Lewan, Paul Lillis, and Paul Trost for insightful reviews, all of which 

improved the manuscript. One of the authors (K.M.) was supported by a Japan Society for the Promotion 

of Science (JSPS) Postdoctoral Fellowship for Research Abroad (1998-1999).

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as suggested by aqueous pryolysis: Organic Geochemistry, v. 19, p. 141-159. 

Price, L. C. and Le Fever, J., 1994, Dysfunctionalism in the Williston Basin The mid-Madison/Bakken

petroleum system: Bulletin of Canadian Petroleum Geologists, v. 42,

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